/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 */
package org.hibernate.engine;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.ReplicationMode;
import org.hibernate.TransientObjectException;
import org.hibernate.collection.PersistentCollection;
import org.hibernate.event.EventSource;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.proxy.HibernateProxy;
import org.hibernate.type.CollectionType;
import org.hibernate.type.EntityType;
import org.hibernate.type.Type;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A session action that may be cascaded from parent entity to its children
 *
 * @author Gavin King
 */
public abstract class CascadingAction {

	private static final Logger log = LoggerFactory.getLogger( CascadingAction.class );


	// the CascadingAction contract ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * protected constructor
	 */
	CascadingAction() {
	}

	/**
	 * Cascade the action to the child object.
	 *
	 * @param session The session within which the cascade is occuring.
	 * @param child The child to which cascading should be performed.
	 * @param entityName The child's entity name
	 * @param anything Anything ;)  Typically some form of cascade-local cache
	 * which is specific to each CascadingAction type
	 * @param isCascadeDeleteEnabled Are cascading deletes enabled.
	 * @throws HibernateException
	 */
	public abstract void cascade(
			EventSource session,
			Object child,
			String entityName,
			Object anything,
			boolean isCascadeDeleteEnabled) throws HibernateException;

	/**
	 * Given a collection, get an iterator of the children upon which the
	 * current cascading action should be visited.
	 *
	 * @param session The session within which the cascade is occuring.
	 * @param collectionType The mapping type of the collection.
	 * @param collection The collection instance.
	 * @return The children iterator.
	 */
	public abstract Iterator getCascadableChildrenIterator(
			EventSource session,
			CollectionType collectionType,
			Object collection);

	/**
	 * Does this action potentially extrapolate to orphan deletes?
	 *
	 * @return True if this action can lead to deletions of orphans.
	 */
	public abstract boolean deleteOrphans();


	/**
	 * Does the specified cascading action require verification of no cascade validity?
	 *
	 * @return True if this action requires no-cascade verification; false otherwise.
	 */
	public boolean requiresNoCascadeChecking() {
		return false;
	}

	/**
	 * Called (in the case of {@link #requiresNoCascadeChecking} returning true) to validate
	 * that no cascade on the given property is considered a valid semantic.
	 *
	 * @param session The session witin which the cascade is occurring.
	 * @param child The property value
	 * @param parent The property value owner
	 * @param persister The entity persister for the owner
	 * @param propertyIndex The index of the property within the owner.
	 */
	public void noCascade(EventSource session, Object child, Object parent, EntityPersister persister, int propertyIndex) {
	}

	/**
	 * Should this action be performed (or noCascade consulted) in the case of lazy properties.
	 */
	public boolean performOnLazyProperty() {
		return true;
	}


	// the CascadingAction implementations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * @see org.hibernate.Session#delete(Object)
	 */
	public static final CascadingAction DELETE = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace("cascading to delete: " + entityName);
			}
			session.delete( entityName, child, isCascadeDeleteEnabled, ( Set ) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// delete does cascade to uninitialized collections
			return CascadingAction.getAllElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			// orphans should be deleted during delete
			return true;
		}
		public String toString() {
			return "ACTION_DELETE";
		}
	};

	/**
	 * @see org.hibernate.Session#lock(Object, LockMode)
	 */
	public static final CascadingAction LOCK = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to lock: " + entityName );
			}
			session.lock( entityName, child, LockMode.NONE/*(LockMode) anything*/ );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// lock doesn't cascade to uninitialized collections
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			//TODO: should orphans really be deleted during lock???
			return false;
		}
		public String toString() {
			return "ACTION_LOCK";
		}
	};

	/**
	 * @see org.hibernate.Session#refresh(Object)
	 */
	public static final CascadingAction REFRESH = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to refresh: " + entityName );
			}
			session.refresh( child, (Map) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// refresh doesn't cascade to uninitialized collections
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			return false;
		}
		public String toString() {
			return "ACTION_REFRESH";
		}
	};

	/**
	 * @see org.hibernate.Session#evict(Object)
	 */
	public static final CascadingAction EVICT = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to evict: " + entityName );
			}
			session.evict(child);
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// evicts don't cascade to uninitialized collections
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			return false;
		}
		public boolean performOnLazyProperty() {
			return false;
		}
		public String toString() {
			return "ACTION_EVICT";
		}
	};

	/**
	 * @see org.hibernate.Session#saveOrUpdate(Object)
	 */
	public static final CascadingAction SAVE_UPDATE = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to saveOrUpdate: " + entityName );
			}
			session.saveOrUpdate(entityName, child);
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// saves / updates don't cascade to uninitialized collections
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			// orphans should be deleted during save/update
			return true;
		}
		public boolean performOnLazyProperty() {
			return false;
		}
		public String toString() {
			return "ACTION_SAVE_UPDATE";
		}
	};

	/**
	 * @see org.hibernate.Session#merge(Object)
	 */
	public static final CascadingAction MERGE = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to merge: " + entityName );
			}
			session.merge( entityName, child, (Map) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// merges don't cascade to uninitialized collections
//			//TODO: perhaps this does need to cascade after all....
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			// orphans should not be deleted during merge??
			return false;
		}
		public String toString() {
			return "ACTION_MERGE";
		}
	};

	/**
	 * @see org.hibernate.classic.Session#saveOrUpdateCopy(Object)
	 */
	public static final CascadingAction SAVE_UPDATE_COPY = new CascadingAction() {
		// for deprecated saveOrUpdateCopy()
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to saveOrUpdateCopy: " + entityName );
			}
			session.saveOrUpdateCopy( entityName, child, (Map) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// saves / updates don't cascade to uninitialized collections
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			// orphans should not be deleted during copy??
			return false;
		}
		public String toString() {
			return "ACTION_SAVE_UPDATE_COPY";
		}
	};

	/**
	 * @see org.hibernate.Session#persist(Object)
	 */
	public static final CascadingAction PERSIST = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to persist: " + entityName );
			}
			session.persist( entityName, child, (Map) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// persists don't cascade to uninitialized collections
			return CascadingAction.getAllElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			return false;
		}
		public boolean performOnLazyProperty() {
			return false;
		}
		public String toString() {
			return "ACTION_PERSIST";
		}
	};

	/**
	 * Execute persist during flush time
	 *
	 * @see org.hibernate.Session#persist(Object)
	 */
	public static final CascadingAction PERSIST_ON_FLUSH = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to persistOnFlush: " + entityName );
			}
			session.persistOnFlush( entityName, child, (Map) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// persists don't cascade to uninitialized collections
			return CascadingAction.getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			return true;
		}
		public boolean requiresNoCascadeChecking() {
			return true;
		}
		public void noCascade(
				EventSource session,
				Object child,
				Object parent,
				EntityPersister persister,
				int propertyIndex) {
			if ( child == null ) {
				return;
			}
			Type type = persister.getPropertyTypes()[propertyIndex];
			if ( type.isEntityType() ) {
				String childEntityName = ( ( EntityType ) type ).getAssociatedEntityName( session.getFactory() );

				if ( ! isInManagedState( child, session )
						&& ! ( child instanceof HibernateProxy ) //a proxy cannot be transient and it breaks ForeignKeys.isTransient
						&& ForeignKeys.isTransient( childEntityName, child, null, session ) ) {
					String parentEntiytName = persister.getEntityName();
					String propertyName = persister.getPropertyNames()[propertyIndex];
					throw new TransientObjectException(
							"object references an unsaved transient instance - " +
							"save the transient instance before flushing: " +
							parentEntiytName + "." + propertyName + " -> " + childEntityName
					);

				}
			}
		}
		public boolean performOnLazyProperty() {
			return false;
		}

		private boolean isInManagedState(Object child, EventSource session) {
			EntityEntry entry = session.getPersistenceContext().getEntry( child );
			return entry != null && (entry.getStatus() == Status.MANAGED || entry.getStatus() == Status.READ_ONLY);
		}

		public String toString() {
			return "ACTION_PERSIST_ON_FLUSH";
		}
	};

	/**
	 * @see org.hibernate.Session#replicate(Object, org.hibernate.ReplicationMode)
	 */
	public static final CascadingAction REPLICATE = new CascadingAction() {
		public void cascade(EventSource session, Object child, String entityName, Object anything, boolean isCascadeDeleteEnabled)
		throws HibernateException {
			if ( log.isTraceEnabled() ) {
				log.trace( "cascading to replicate: " + entityName );
			}
			session.replicate( entityName, child, (ReplicationMode) anything );
		}
		public Iterator getCascadableChildrenIterator(EventSource session, CollectionType collectionType, Object collection) {
			// replicate does cascade to uninitialized collections
			return getLoadedElementsIterator(session, collectionType, collection);
		}
		public boolean deleteOrphans() {
			return false; //I suppose?
		}
		public String toString() {
			return "ACTION_REPLICATE";
		}
	};


	// static helper methods ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * Given a collection, get an iterator of all its children, loading them
	 * from the database if necessary.
	 *
	 * @param session The session within which the cascade is occuring.
	 * @param collectionType The mapping type of the collection.
	 * @param collection The collection instance.
	 * @return The children iterator.
	 */
	private static Iterator getAllElementsIterator(
			EventSource session,
			CollectionType collectionType,
			Object collection) {
		return collectionType.getElementsIterator( collection, session );
	}

	/**
	 * Iterate just the elements of the collection that are already there. Don't load
	 * any new elements from the database.
	 */
	public static Iterator getLoadedElementsIterator(SessionImplementor session, CollectionType collectionType, Object collection) {
		if ( collectionIsInitialized(collection) ) {
			// handles arrays and newly instantiated collections
			return collectionType.getElementsIterator(collection, session);
		}
		else {
			// does not handle arrays (thats ok, cos they can't be lazy)
			// or newly instantiated collections, so we can do the cast
			return ( (PersistentCollection) collection ).queuedAdditionIterator();
		}
	}

	private static boolean collectionIsInitialized(Object collection) {
		return !(collection instanceof PersistentCollection) || ( (PersistentCollection) collection ).wasInitialized();
	}

}